Implant having attacment and hole-insert parts, and method for producing such an implant

ABSTRACT

An implant ( 1 ) has attachment and hole-insert parts ( 2, 3 ) with an outer surface or outer surfaces having external layer arrangements ( 6, 7 ). The implant can be provided in a known manner with threads ( 3   a,    3   b ) on cylindrical and conical portions. The implant is made in principle in two production stages. In a first production stage, the outer surface or outer surfaces ( 6   a ) of the implant are given a relatively high roughness value and/or a relatively high degree of porosity. In a second stage, the uneven or porous surface thus obtained is coated with an oxide layer ( 7 ) which can be uniform or can have different thicknesses along the longitudinal and/or circumferential directions(s) of the implant. In one embodiment, the oxide layer ( 7 ) can be coated with a bone-growth agent or bone-growth-promoting agent and/or calcium phosphate ( 16 ), for example by means of chemical deposition, dipping or sputtering.

[0001] The present invention relates to an implant having attachment andhole-insert parts provided with one or more outer surfaces having one ormore layer arrangements. The invention also relates to a method forproducing external layer arrangements on one or more outer surfaces ofan implant with attachment and hole-insert parts.

[0002] There are a great many implants of this type. Reference may bemade, for example, to the implant according to WO 97/43976 from the sameapplicant as the present invention. Reference may also be made, forexample, to the implant according to WO 97/03621. Reference may also bemade to the Swedish patent applications from the same applicant as thepresent application, bearing numbers 9901971-3, 9901973-9 and 9901974-7.Reference may also be made to U.S. Pat. specifications Nos. 5,571,017,5,842,865, 5,885,079, 5,947,735 and 5,989,027.

[0003] A characteristic feature of an implant can be that it has anattachment part which is intended to extend up through the jaw bone topermit connection, via a spacer element, of a superstructure for theimplant. In the case of what is known as a self-tapping implant, thelatter is provided with one or more outer threads which can have acylinder shape or cone shape. From some of the above referencedocuments, it is also known to produce implants with surfaces ofdifferent roughness values and/or porosities.

[0004] In the type of implant in question, there is a need to be able tooffer a wide range of implants based on the same manufacturingtechnique. In some cases it may be of advantage to use outwardly poroussurfaces or surface areas where the porosity has to satisfy differentscrewing procedures with different bone density of the jaw bone or toothbone in question. In soft jaw bone, it may be desirable to use a coarserporosity, whereas in hard bone structures in the jaw and tooth bone itmay be advantageous to use lower degrees of porosity or to useprecision-worked or precision-machined surfaces which offer lessresistance during screwing. In some cases it may also be advantageous toinsert a barrier in order to prevent so-called ion release. In dentistryit is advantageous in some cases to be able to provide porosities ofdifferent degrees in order to increase the surface areas for bone union.In other cases it is important to reduce the roughness value/porosity ofsaid surfaces. In cases where the porosities are used as depots forbone-growth agents or bone-growth promoting agents, it is expedient tobe able to offer depots of greater or lesser extent or smooth surfaceson which, for example, calcium phosphate is to be applied. It is anobject of the invention to solve the problems mentioned above.

[0005] It is preferable for the proposed solutions to be able to followaccepted and well-proven methods to establish a choice of porosities,smooth surfaces, coatings, etc. The invention solves this problem too.

[0006] That which can principally be regarded as characterizing animplant according to the invention is that one or more arrangements havea machined or treated surface with a high roughness value and/orporosity and an outer oxide layer applied on top of this surface.

[0007] In one embodiment of the inventive concept, the oxide layer has athickness in the range of from 5 nm to 20 μm. The oxide layer can inthis case have a thickness varying along the longitudinal and/orcircumferential direction(s) of the implant. In one embodiment, a layerof calcium phosphate can be applied on top of the oxide layer.

[0008] A method according to the invention is characterized in that theimplant is machined and/or treated to produce a high roughness value ora preferably high porosity on the surface or surfaces, and in that saidsurface or surfaces are thereafter coated with an oxide layer. The oxidelayer can be obtained with the aid of electrochemical treatment in whichthe surface or surfaces of the implant are dipped in an electrolyte, inwhich an anode and cathode arrangement is provided. To establish saidporosity, a voltage is applied to the anode and cathode arrangement, anda current produced by the voltage is led via the electrolyte and theimplant dipped in the latter. With this method, a high porosity can beobtained if the voltage assumes a relatively high value, for example avalue of 300 volts or more, and a certain type of electrolyte is used.In a possible second stage, the oxide layer can be applied in a similarmanner, the implant being dipped in the same electrolyte or in anotherelectrolyte, and the voltage value being chosen at a lower level so thatthe oxide layer is established with a lower degree of porosity or aporosity which is almost zero. Such a smoother oxide layer can also beproduced by heat treatment of the implant in an oxygen-containingatmosphere.

[0009] Further developments of said implant and method are set out inthe attached subclaims concerning the implant and the method,respectively.

[0010] The method proposed above makes it possible to produce a range ofimplants with different porosities, porosity extents, treated surfaces,etc. From this range it is possible to choose the implant which is bestsuited for the treatment situation in question. The quality of the bonein question, for example jaw bone or tooth bone, varies greatly in thesame individual and between different individuals. The bone structure ofthe upper jaw is relatively soft, whereas the bone structure of thelower jaw can vary from a relatively soft structure to a hard structureat the front of the jaw. Implants of greater or lesser porosity can thusbe produced and, similarly, oxide layers with a fine surface structurecan be applied on top of the already existing surface with a highroughness value or porosity. Ion release can be limited in this way, andthe smoother surface can also constitute a substrate surface for layershaving bone-growth agents or bone-growth-promoting agents. The oxidelayer applied on top of the uneven or porous surface can consist of athin or relatively thick oxide layer which can be applied in a knownmanner by simple dipping in a voltage-connected electrolyte in a mannerknown per se. The form and thickness of the oxide layer can be varied.Thus, for example, the oxide layer can have a greater thickness at thecentral or outer parts of the implant. The oxide layer can be appliedhere and there on the porous outer surface in question. Alternatively,the oxide layer can be varied in thickness in the circumferentialdirection of the implant, and so on.

[0011] A presently proposed embodiment of an implant and of a methodaccording to the invention will be described below with reference to theattached drawings, in which:

[0012]FIG. 1 is a vertical section showing an implant applied in apartly shown tooth or jaw bone,

[0013]FIG. 2 is an enlarged longitudinal section showing the outer partof a thread on the implant according to FIG. 1, from which it will beseen that the outer surface of the thread has been provided with layersaccording to the invention,

[0014]FIG. 3 is a diagram showing voltages and currents which arise inan electrochemical method on an implant dipped in an electrolyte, and

[0015]FIG. 4 is a vertical section and schematic representation showingthe implant according to FIG. 1 dipped in an electrolyte, and an anodeand cathode arrangement provided in the latter.

[0016] An implant of the type specified above is indicated by 1 in FIG.1, i.e. an implant which can be found in the prior art and is describedinter alia in the documents referred to above. The implant has anattachment part 2, for example for a spacer element, and a hole-insertpart 3. The outer surface 2 a of the attachment part can be smooth orprecision-worked (for example machined) or can have a greater or lesserporosity. At the top, the hole-insert part 3 can have a cylindricalportion with outer thread 3 a, and a conical portion with outer thread 3b at the free/lower end of the implant. The implant is of the so-calledself-tapping type and can be screwed into a hole 4 in a bone, forexample a tooth bone or jaw bone. In the present case, the surface layerof the threaded portions has a relatively high roughness value/porositycreated, for example, by etching or shot-peening which are known per se.In accordance with the invention, an oxide layer as described below isapplied on the outside of said relatively rough and porous layers.

[0017] In FIG. 2, the layer with the high roughness value is indicatedby 6 and the outer oxide layer is indicated by 7. As has already beenmentioned, the layer 6 can be created by etching or shot-peening of theimplant part in question. The layer 6 can have a surface roughness ofbetween 0.4 and 5 μm. The thickness t of the outer oxide layer 7 assumesvalues preferably in the range of from 4-5 nm to ca. 20 μm. The layercan be very porous with 1×10⁷- 1×10¹⁰ pores/cm². In a preferredembodiment, the porosity is considerably lower in the outer oxide layer7.

[0018] Methods which are known per se can be used for applying saidlayer 7. In the present case, the electrochemical method is preferablyused which is described in the abovementioned Swedish patentapplications 9901971-3 and 9901974-7. A voltage/current ratio inaccordance with the figure occurs in such an electrochemical method. Asthis method is already known per se, it will not be described here, butreference may be made to said Swedish patent applications. As can beseen from FIG. 3, a voltage rise takes place according to curve 9, and acurrent 10 has at the outset a substantially constant value and after atime drops in accordance with curve part 10 a. The formation of thetitanium oxide layer and its final properties and structures aredetermined by a number of parameters in said process. Thus, thecomposition of the electrolyte and its temperature, the applied voltageand current, the electrode geometry and the treatment time, etc., affectthe thickness, degree of porosity, etc., in the titanium oxide layer tobe created. Oxide thicknesses and porosities can thus be varied with theaid of said parameters. For example, when the layer 7 has a substantialthickness according to FIG. 2, a relatively high voltage, for example avoltage of 300 volts, will be used. A constant current (of curve part10) is of the order of magnitude of 0.2 ampere. It has been found thatas the voltage rises towards said order of magnitude, a certain sparkformation occurs at the electrolyte surface and between the electrolyteand the outer surface part in question. This spark formation can be usedto eliminate burrs which arise during machining of the inner surface 8of the implant. This removal of burrs is symbolized by 11 in FIG. 2.

[0019]FIG. 4 shows those parts of the implant which are to be providedwith the oxide layer 7 being dipped in an electrolyte 12 in accordancewith the abovementioned known electrochemical method. In this case, theimplant functions principally as an anode in a combined anode andcathode arrangement in which the cathode part has been symbolized by 13.An energy source is indicated by 14 and the negative potential 14 a ofthe energy source is connected to the cathode 13 and the positivepotential 14 b is connected to the anode/implant. The connection can beeffected by way of a connection member 15, by means of which thepositive potential 14 is connected to the anode/implant.

[0020] As regards the application of the layer 7, reference is also madeto application XXXX which was filed on the same day and which relates toformation of implants with extended zones in which the porositydecreases continuously within each zone. For production of theunderlying surface layer 6, the implant, for example of titanium, isprovided with an outer surface 6 a with a preferably high roughnessvalue which has been established by means of shot-peening, etching,plasma spraying, etc. In the electrochemical method, the layer 7 is thenproduced with suitable adjustment of said parameters.

[0021] By means of what has been proposed above, different types ofimplants which are based on the same technology can be produced. Thestructures and thicknesses of the layers 6 and 7 can be determinedaccording to the respective dental situation and the purpose of theimplant is to achieve the optimum result. The outer layers 6 or 7 canhave uniform thicknesses around the whole circumference of therespective outer surface. Alternatively, they can extend along onlyparts of the circumference. In a further alternative, the layer 6 canextend along all or part of the circumference and can be covered onlypartially by the outer layer. This also applies to the extents in thelongitudinal or height direction. According to FIG. 2, the outer oxidelayer can be provided on its outer surface 7 a with a coating of calciumphosphate 16 which is sputtered or otherwise applied to said outersurface 7 a once the outer layer 7 has been applied.

[0022] The invention is not limited to the embodiment described above byway of example, and instead it can be modified within the scope of theattached patent claims and the inventive concept.

1. Implant (1) which has attachment and hole-insert parts (2, 3) with anouter surface or outer surfaces (2 a, 3 a, 3 b) having external layerarrangements (6, 7), characterized in that one or more arrangements havea machined or treated inner surface (6 a) with a high roughness valueand/or porosity and an outer oxide layer (7) applied on top of the innersurface.
 2. Implant according to Patent claim 1, characterized in thatthe outer oxide layer (7) has a thickness in the range of 5 nm to 20 μm.3. Implant according to Patent claim 1, characterized in that the outeroxide layer (7) has a thickness varying along the longitudinal and/orcircumferential direction(s) of the implant.
 4. Implant according toPatent claim 1, 2 or 3, characterized in that the arrangement comprisesa bone-growth agent or bone-growth-promoting agent and/or a coating ofcalcium phosphate (16) applied on top of the oxide layer (7).
 5. Implantaccording to any of the preceding patent claims, characterized in thatit comprises one or more outer threads (3 a, 3 b) on said hole-insertpart(s) (3).
 6. Method for producing an external layer arrangement (6, 7and possibly 16) on the outer surface(s) (2 a, 3 a, 3 b) of the implantwith attachment and hole-insert parts, characterized in that the implant(1) is machined and/or treated to produce a high roughness value and/ora high degree of porosity on the outer surface (6 a), and in that themachined and/or treated and/or porous surface (6 a) is thereafter coatedwith an oxide layer (7).
 7. Method according to Patent claim 5,characterized in that the structure of the external layer arrangement(s)is obtained with the aid of electrochemical treatment in which thesurface or surfaces of the implant are obtained by means of electrolyteand an anode and cathode arrangement (13, 14, 14 a, 14 b) to which theimplant (1) is applied, and in that the anode and cathode arrangement isconnected to a voltage so that a current (J) passes through the implant.8. Method according to Patent claim 6, characterized in that the implant(1) is dipped in an electrolyte (12) and in that the current (J) is ledvia electrolyte-coated parts (3 a, 3 b) of the implant (1).
 9. Methodaccording to Patent claim 6 or 7, characterized in that, to establishsaid porosity, the chosen voltage is high, for example 300 volts, and inthat the current thereby obtained causes spark formation (9 a) at thetransition between the electrolyte and the implant and in that, uponsaid spark formation, a burr-eliminating effect (11) is obtained on theouter surface of the implant.
 10. Method according to Patent claim 7, 8or 9, characterized in that the burr-eliminating function is obtained atthe thread or threads (3 a, 3 b) of the implant.
 11. Method according toany of Patent claims 6 to 10, characterized in that the surface orsurfaces (3 a, 3 b) which bear said oxide layer (7) are machined with ahigh roughness value, for example by means of shot-peening.
 12. Methodaccording to any of the preceding patent claims, characterized in thatsaid oxide layer (7) is given a thickness of 5 nm to 20 μm.
 13. Methodaccording to any of Patent claims 6 to 12, characterized in that abone-growth agent or bone-growth-promoting agent and/or calciumphosphate (16) on top of the oxide layer (7) is applied by means of wetchemical deposition or sputtering.
 14. Method according to any of Patentclaims 6 to 12, characterized in that the bone-growth agent orbone-growth-promoting agent (16) on top of the oxide layer (7) isapplied by means of dipping the implant in said agent.